The Dimensions of a Pioneering Strategy

Two Classmates Paired
To Test Academic Ideas;
Investors' 'Boot Camp'

Nestled by the Pacific Ocean, in Santa Monica, Calif., money-management firm Dimensional Fund Advisors Inc. may be one of the mutual-fund world's least known revolutionaries.

For 25 years, Dimensional has walked a path between "active" money management -- in which stock pickers use research to choose individual shares for a portfolio -- and the passive investment style of Vanguard Group, which is best known for funds that...